Suppose we have a circuit with and EMF source and a resistor. We know that when electron moves from one terminal of a voltage source to another it encounters resistance, which is basically collisions with stationary positive ions. During the collisions some of the electric potential energy and kinetic energy that electron has is passed in form of kinetic energy to the atoms of the material of the conductor. That means they lose some of their own kinetic energy, i.e. they're being slowed down. It seems reasonable to think that the electric current (charge per unit time) is changing, as the electrons slow down due to the collisions. Why then we still get a constant current? What is the flaw in what I've described?
Electrons must accelerate and gain a bigger velocity in medium with lower resistance. It seems reasonable for me to think that electrons are moving faster where the resistance is lower and slower where it is higher. So if we have zones with different resistances, electrons will move with different speed and thus the current will vary.